Spring cannulae

ABSTRACT

Disclosed herein are embodiments of spring cannulae, including one or more holes in the sidewall of the cannula. Some disclosed cannulae include a wire, helically wound to form coils, and at least one hole in the cannula that interrupts one or more of the coils. Some embodiments further include a fused region of the coils through which the hole passes. Some embodiments include a ring attached to ends of the interrupted coils, where the hole is surrounded by the ring. Some embodiments include a sheath that is attached to a radial surface of the interrupted coils, where the hole passes radially though the sheath.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/107,404, filed Jun. 16, 2015, now U.S. Pat. No. 10,226,595, which isthe U.S. National Stage of International Application No.PCT/US2015/036005, filed Jun. 16, 2015, which claims the benefit of U.S.Patent Application No. 62/012,817, filed Jun. 16, 2014, the entiredisclosures all of which are incorporated by reference.

FIELD

This disclosure relates to embodiments of spring cannulae having one ormore holes in the sidewall to allow passage of a fluid through thesidewall, and to methods of manufacturing such spring cannulae. Morespecifically, spring cannulae according to embodiments of the inventioncan be used to draw blood from or to introduce blood to a patient duringa surgical procedure where a cardiopulmonary bypass is utilized. Forexample, the spring cannulae can be positioned at or near a right atriumof the patient's heart to remove venous blood from the patient foroxygenation.

BACKGROUND

It is a routine requirement of a variety of surgical procedures toutilize extracorporeal cardiopulmonary bypass in order to mechanicallyperform the functions normally conducted by the heart and lungs. Venousblood depleted in oxygen and rich in carbon dioxide is removed from thepatient and pumped to an oxygenating apparatus in order to oxygenate theblood and remove excess carbon dioxide. The blood is then returned tothe patient's arterial system.

It is important that adequate volumes of blood be drained from thepatient during cardiopulmonary bypass so that the extracorporeal lifesupport equipment can keep up with the patient's need for oxygen and canadequately remove excess carbon dioxide. Insufficient quantities ofoxygen can lead to serious tissue damage. Inadequate removal of carbondioxide leads to a condition known as “acidosis,” which can result inserious consequences caused by the alternation in normal metabolicfunctioning of critical enzymes. Either condition can result in seriousinjury to the patient.

A general technique involves using a drainage cannula to remove thevenous blood from the patient for extracorporeal treatment. Suchcannulae can have drainage openings at the distal end and also alongtheir length proximal to the distal end. Such cannulae are insertedthrough the right atrium and extend into either the inferior vena cavaor the superior vena cava or both, with the proximal drainage openingspositioned within the right atrium. This placement permits blood to bedrained simultaneously from the right atrium and from surrounding venacavae.

Surgically placed cannulae are frequently used in various surgicalprocedures, such as, but not limited to the procedure described above,to draw blood from or introduce blood into patient vessels. In somecases there is a need for a cannula to have holes in the sidewall toallow blood flow through the sidewall during procedures. In cannulae,such as drainage cannulae, that have a sidewall made from a coiledspring, the holes along the length of the cannula can be formed bycutting the spring and placing a solid-walled tube between the two cutends. Holes can then be punched into the solid-walled section of thecannula. However, this type of cannula design results in a weakness ofthe cannula in the area that has no spring, and the cannula can separateat the joints between the spring and solid-walled tube during use.

SUMMARY

Disclosed herein are embodiments of a spring cannula having one or moreholes in the sidewall. The cannula includes at least one wire that ishelically wound to form a plurality of coils defining a tubular sidewallof the cannula. The cannula further includes one or more holes passingradially through the sidewall, and in some embodiments, the holesinterrupt one or more of the coils. The interrupted coils can bereinforced by being axially coupled to adjacent coils in a regionsurrounding the hole.

In some embodiments, the cannula includes a group of adjacent coils thatare axially fused together, such as by welding, to form a fused regionof the wire, and at least one hole passes radially through the fusedregion of the wire, such that the hole interrupts a plurality of thefused coils. The axial length of the hole can be less than an axiallength of the fused region of the wire. The fused region includes one ormore uninterrupted coils on either axial side of the hole thatreinforces the interrupted coils.

In some embodiments, the cannula includes a ring surrounding the holeand connected to and reinforcing the interrupted coils. The ring can beattached to an inner or an outer surface of the coils, or the ring canbe evenly positioned such that the ring and the coils are at about thesame radial distance from a longitudinal center axis of the cannula. Insome embodiments, a plurality of pieces of metal can be positioned(e.g., welded) in between the ends of the interrupted coils, and thering can be formed from the ends of the interrupted coils together withthe added pieces of metal.

In other embodiments, the cannula can include a reinforcing sheathattached to a radial surface of an adjacent group of the coils, wherethe adjacent group of coils includes the hole, the interrupted coils,and at least one un-interrupted coil at either axial side of theinterrupted coils. The hole passes through the sheath and the coils. Thesheath can be attached to an inner radial surface or an outer radialsurface of the coils. The sheath can be a solid metal tube welded to thecoils, for example, or the sheath can include an inner layer comprisingmetal, and an outer layer comprising a polymer that shrinks over thesheath and coils.

In any of the above embodiments, the cannula can further include apolymeric coating that encases the coils but does not block the hole(s).

In alternative embodiments, a cannula can include a wire that ishelically wound to form a tubular spring comprising a plurality of coilsthat define a sidewall of the cannula and are not interrupted by thesidewall hole(s). The plurality of coils can include one or more coilsthat are elongated in an axial dimension relative to adjacent coils toprovide space therebetween for the hole(s).

In alternative embodiments, a cannula includes a wire and an insert. Thewire is helically wound to form a plurality of coils, wherein theplurality of coils includes at least one coil portion that is wound at asmaller angle relative to a central axis of the cannula than adjacentcoils positioned at opposite ends of the at least one coil portion, suchthat the at least one coil portion is stretched axially relative to theadjacent coils. The insert includes a porous section defining at leastone hole passing radially through the insert, wherein the insert ispositionable between the adjacent coils and the at least one coilportion is positionable on the insert and is spaced apart from the atleast one hole.

In some embodiments, a method of manufacturing the above cannulaincludes winding the wire to form the plurality of coils and the atleast one coil portion, positioning the insert corresponding to the atleast one coil portion between the adjacent coils heating a regionaround the insert to bond the insert with the wire; and heating theentire cannula to seal gaps between adjacent ones of the plurality ofcoils.

The foregoing and other objects, features, and advantages of thedisclosed technology will become more apparent from the followingdetailed description, which proceeds with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a spring cannula having a wire body withporous regions according to a first embodiment.

FIG. 2 is a perspective view of a portion of the wire body of the springcannula of FIG. 1 where a coating is partially cut away to show coils ofthe wire body.

FIG. 3 is a perspective view of a portion of a wire body of a springcannula according to an embodiment in which a porous region comprises afused region.

FIGS. 4A-4B are perspective views of a portion of the wire body shown inFIG. 3, illustrating the fused region prior to and after formingsidewall holes in the fused region.

FIG. 5 is a perspective view of a portion of a wire body of analternative spring cannula in which a porous region comprises rings andwhere the wire body is encased in a coating which is partially cut awayto show coils of the wire body.

FIG. 6A-6B are perspective views of a portion of the wire body shown inFIG. 5, illustrating the position of the rings on the coils before andafter sidewall holes are made within the rings.

FIG. 7 is a perspective view of a portion of a wire body of anotheralternative spring cannula in which the porous region is covered in asheath overlaying coils of the wire body, where the wire body is encasedin a coating which is partially cut away to show the coils.

FIG. 8 is a perspective view of the coils and sheath of the cannula ofFIG. 7 before sidewall holes are formed through the coils.

FIG. 9 is a perspective view of a portion of a wire body of anotheralternative spring cannula in which a porous region comprises anelongated coil and a coating having holes.

FIG. 10 is a side view of a portion of the spring cannula of FIG. 9coiled onto a mandrel, with some of the coils spaced apart axially toprovide space therebetween for formation of sidewall holes.

FIG. 11 is a perspective view of a distal portion of a spring cannulaaccording to yet another embodiment in which the porous portions aretransition sections.

FIGS. 12A-12B are perspective views of transition sections that can beused with the spring cannula of FIG. 11.

FIGS. 13A-13D show a method of making the spring cannula of FIG. 11.

FIGS. 14A-14D show an alternative method of making the spring cannula ofFIG. 11.

FIGS. 15A-15B shows a modification of the steps of FIGS. 14B-14C inwhich a clamp is included over the transition section.

FIG. 16A is a perspective view of a distal portion of another springcannula including a transition section having an extended body.

FIG. 16B is a perspective view of the extended body of the transitionsection of FIG. 16A.

FIG. 17 is a flowchart of a method of manufacturing the spring cannulaeof FIGS. 11 and 16A-16B.

FIG. 18 is a flowchart of an alternative method of manufacturing thespring cannulae of FIGS. 11 and 16A-16B.

DETAILED DESCRIPTION

The present disclosure provides improved cannula designs, particularlyfor spring cannulae that have a wire body (such as a helically coiledwire body or spring) with at least one porous region having one or moreholes in sidewalls of the porous region. Previous cannula designsincluded a solid-walled section inserted between two cut ends of acoiled spring, with sidewall holes being formed in the solid-walledsection. However, this design has points of weakness at the joints wherethe ends of the spring are attached to the ends of the solid-walledsection, which can result in kinks or breakages of the cannula at thosepoints during use. The embodiments disclosed herein offer a stronger andmore reliable solution to cannula design to reduce or prevent cannulabreakage. Some disclosed embodiments include a hole that cuts throughthe coils of the spring. However, these embodiments includereinforcement of the cut spring coils proximal to the hole, such thatthe interrupted coils, those coils that have been cut to make the hole,are supported and reinforced to prevent breakage or the formation ofkinks adjacent to the hole. Some embodiments include transition sectionshaving holes that are inserted between the coils of the wire bodywithout cutting the coils adjacent to the transition sections such thatthe coils of the wire body are continuous through the transitionsections. The continuous coil design allows the catheter to be moreeasily retrievable than prior cut designs where there was a risk ofbreakage at the cut points. The continuous coil design also reduces thepotential for exposure to cut edges at the coil ends.

FIG. 1 shows a spring cannula 2 having a wire body 9 with porous regions16.

The spring cannula 2 is made of a continuous helically coiled wire 4that extends from a distal end having a tip 1 to a proximal end having aconnector 3. The wire 4 can be a flat wire and can have a diameter of0.008 inches. The portion of the spring cannula 2 that includes the wire4 is referred to as the wire body 9. The spring cannula 2 can be formedfrom at least one wire 4, helically wound around a central axis 6 toform a plurality of coils 8. The tip 1 is flexible and can have asmaller diameter than the wire body 9 to facilitate insertion and/oradvancement of the tip 1, for example, through a patient's body and intothe heart or a superior or inferior vena cava of the patient duringsurgery. The tip 1 can also include holes to allow blood flow throughthe tip 1 during medical procedures. For example, the tip 1 can includedrainage holes to collect blood from the vena cava during surgery, suchas during cardiopulmonary bypass surgery.

The connector 3 has threads 5 to correspond to threads of tubing oradditional devices for use with the cannula 2 during surgery. Forexample, the threads 5 can correspond to threads on an intake tube of acardiopulmonary bypass machine. In such an embodiment, when the springcannula 2 is connected to the cardiopulmonary bypass machine and themachine is in use, blood is collected by the spring cannula 2 andcirculated through the bypass machine to remove carbon dioxide and tooxygenate the blood prior to the blood being returned to the body. Anyother connection means suitable for such a connection can also be usedin other embodiments.

In FIG. 1, the wire body 9 includes three porous regions 16 flanked byfour wire reinforced regions 7. However, the number of porous regions 16and wire reinforced regions 7 can vary in other embodiments. Forexample, in some embodiments, there are only two porous regions andthree wire reinforced regions surrounding the porous regions. In otherembodiments, there is only one porous region. In other embodiments,there can be more than three porous regions. In addition, the porousregions need not be flanked by wire reinforced regions. For example, theporous region closest to the tip of the spring cannula can be directlyadjacent to the tip without a wire reinforced region therebetween.

Each porous region 16 includes one or more holes 18. In the illustratedembodiment, in each of the porous regions 16, three holes 18 are evenlyspaced circumferentially and the holes 18 are axially aligned. However,the number of holes 18 in a porous region 16 can vary depending on theapplication, and in some embodiments the holes 18 are not axiallyaligned. For example, two or more holes can be adjacent or aligned alongthe central axis 6 of the spring cannula 2. In some embodiments, theorganization of the holes in each of the porous regions can vary fromone another. In addition, the holes can vary in size and shape.

The spring cannula 2 also has an overcoat 11. The overcoat 11 can bemade of a thermoplastic polyurethane elastomer (TPU). For example, theovercoat 11 can be made of Tecothane™. The overcoat 11 can cover theentire spring cannula 2, including the tip 1, the wire body 9 and theconnector 3, thereby integrating the tip 1, the wire body 9 and theconnector into one continuous cannula, or it can cover portions of thecannula 2, such as the tip 1 and the wire body 9, but not the connector3. However, in some embodiment, the overcoat 11 may not be needed andcan be omitted. In some of the following illustrative embodiments, theovercoat 11 has been omitted to facilitate depiction of the underlyingstructures. In some embodiments, the wire 4 that forms the spring coils8 has an additional coating 14, as shown in FIG. 3. The coating 14 canbe a polymeric material, for example, a thermoplastic polyurethaneelastomer such as Pellethane®, that is coated on the wire 4 before thewire 4 is wound to form the wire body 9. After winding, the coated wirecan be heat-treated such that the polymeric coating on each coil bondsor fuses with the coating on the adjacent coils and forms thesubstantially continuous, flexible coating 14 that encases the coils 8.The coating 14 can be used in addition to, or alternative to, theovercoat 11.

In any of the embodiments disclosed herein, the wire 4 can be made fromany suitable material, such as stainless steel (such as 304V stainlesssteel wire), nitinol, or other biocompatible metals. Some embodimentscan comprise two or more discrete wires that are helically woundtogether. The plural wires can be wound in parallel with each other,such as with two wires forming a double helix, or the wires can be woundin opposing directions. The additional wire(s) can provide advantagescompared to single-wire embodiments, such as providing better torque forthe cannula, improving the strength of the cannula while stillmaintaining flexibility, and providing redundancy in the event that onewire should fail.

FIG. 2 shows a portion of the wire body 9 of the spring cannula 2 ofFIG. 1 where the coating 14 is partially cut away to more clearly showthe coils 8 of the wire body 9.

The coils 8 collectively define a radially inner surface 10 and aradially outer surface 12 of the cannula 2. The coils 8 provideflexibility and strength to the spring cannula 2, helping to preventkinking and breakage while allowing for flexible movement duringsurgery.

As discussed above, the wire 4 can comprise stainless steel, forexample. In some embodiments, the wire 4 is coated with a polymericcoating that is applied to the wire 4 before it is wound to form thecoils 8. After the coils 8 are wound, the wire 4 can be heat-treatedsuch that the polymeric coating melts to form the continuous coating 14(partially cut away at front left of FIG. 1 to show the coils) thatencases the coils 8, and forms the wire body 9 of the cannula 2.

FIG. 3 shows a portion of a wire body 9 of a spring cannula 2 in whichat least one of the porous regions 16 comprises a fused region.

In this embodiment, the spring cannula 2 includes the fused region 16,formed by fusing a plurality of coils 8 together (see, e.g., FIG. 4A).The coils 8 are compressed together in the fused region 16 so that thesides of each adjacent coil touch and/or are fused together, forming arelatively more rigid tubular section. The fused region 16 can be formedby removing the polymeric coating 14 from the area of the coils to befused, and welding the exposed areas of the coils together. The coilscan alternatively be fused together in other ways such as by bondingwith an adhesive. One or more holes 18 (three in the illustratedembodiment of FIG. 4B) can be formed in the fused region 16 (partiallyor entirely in the fused region), by cutting through and interrupting aplurality of the fused coils. Even though several coils 8 are cut andinterrupted in the fused region 16, the region maintains structuralintegrity because some of the fused coils (e.g., the coils at the axialends of the fused region) are not interrupted and reinforce theinterrupted coils. The polymeric coating 14 can optionally be re-formedover the fused region 16, but not over the holes 18. The holes 18 can beformed by any suitable means, such as punching, or cutting, for exampleby a laser. The fused region 16 is formed from sufficient coils 8 tohave an axial length 20 that is greater than an axial length 22 of theholes 18 (FIG. 4B). In the illustrated embodiment, the three holes 18are evenly spaced circumferentially and are axially aligned. However,the number of holes in a fused region can vary depending on theapplication, and in some embodiments the holes are not axially aligned.Additionally, a cannula can have multiple fused regions 16 as shown inFIG. 3, each with one or more holes 18.

FIGS. 5 to 6B show a portion of a wire body 109 of an alternative springcannula 100 in which a porous region 116 comprises rings 115 and wherethe wire body 109 is encased in a coating 114, which is partially cutaway in FIG. 5 to more clearly show coils 108 of the wire body 109.

The alternative spring cannula 100 is shown having holes 118 in itssidewall. The cannula 100 can be formed from one or more wires 104,helically wound around a central axis 106 to form a plurality of coils108. In some embodiments, the wire 104 is a stainless steel wire. Insome embodiments, the wire 104 is coated with a polymeric coating,applied to the wire before it is wound to form the coils 108. The coils108 collectively define a radially inner surface 110 and a radiallyouter surface 112 of the cannula 100. After the coils are wound, thewire can be heat-treated such that the polymeric coating melts to form acoating 114 (partially cut away in front to show the coils) that encasesthe coils 108, and forms the cannula 100.

One or more rings 115 can be attached to, or formed between, the coils106, as shown in FIG. 6A, in order to reinforce the holes 118. Thepolymeric coating 114 can be removed from the portion of the coils 108that are attached to the rings 115. In some embodiments, the rings 115can be attached to either the inner surface 110 or the outer surface 112of a group of adjacent coils 108. In such embodiments, each ring 115 canbe attached, such as by welding, to each coil 108 in the group ofadjacent coils at each point of contact between the ring 115 and eachcoil 108.

As shown in FIG. 6B, the holes 118 can be formed within the rings 115and pass radially through the coils 108, such that each hole interruptsthe group of adjacent coils attached to the respective ring. Each hole118 is enclosed within a ring 115, such that the inner dimensions of thering correspond to the dimensions of the hole, and the ring 115 isattached to the ends of the coils 108 that are interrupted by the hole.

In some embodiments, one or more rings 115 can be placed or formed evenwith the coils 108 such that a radial distance from the central axis 106to the inner side of the ring is substantially the same as a radialdistance from the central axis 106 to the inner surface 110 of thecoils. In some embodiments, pieces of metal are placed in between andattached to (e.g., by welding) the ends of the interrupted coils, suchthat the pieces of metal together with the ends of the interrupted coilsform the ring 115. In other embodiments, a hole can be cut thatinterrupts the coils and then a fully annular ring can be placed withinthe hole, such that the ends of the interrupted coils are in contactwith the perimeter of the annular ring. The ring can be attached to theends of the interrupted coils by welding or otherwise.

The rings 115 can be formed from the same material as the wire 104, orfrom a different material. There can be one or more rings 115 attachedto the wire 104. In the illustrated embodiment there are three rings 115(FIG. 6A). The polymeric coating 114 can optionally be reformed over thecut coils and the ring, but not over the holes 118.

FIG. 7 shows a portion of a wire body 209 of another alternative springcannula 200 in which the porous region 216 is covered in a sheath 213overlaying coils 208 of the wire body 209.

The spring cannula 200 is shown having holes 218 in its sidewall. Thecannula 200 can be formed from one or more wires 204 wound helicallyabout a central axis 206 to form a plurality of coils 208. In someembodiments, the wire 204 comprises stainless steel. In someembodiments, the wire is coated with a polymeric coating, applied to thewire before it is wound to form the coils 208. The coils 208collectively define a radially inner surface 210 and a radially outersurface 212 of the cannula 200. After the coils are wound, the wire canbe heat-treated such that the polymeric coating melts to form a coating214 (partially cut away in FIG. 7 to show the coils) that encases thecoils 208, and forms the cannula 200.

As shown in FIG. 7, the cannula 200 includes a sheath 213 connected tothe outer surface 212 of a group of adjacent coils 208. In analternative embodiment, the sheath 213 is connected to the inner surface210 of the coils 208. A portion of the coating 214 can be removed toallow connection between the sheath 213 and the wire 204. The sheath 213can be made from the same material as the wire 204, such as fromstainless steel, or it can be made from a different material. In someembodiments, the sheath 213 is welded to the wire 204, such as by laserwelding. In other embodiments, an adhesive is used to attach the sheath213 to the wire 204.

In some embodiments, the sheath 213 comprises at least one additionallayer, such as in a dual layer sheath, including a polymeric layer. Sucha sheath 13 can include an inner metal layer and an outer polymericlayer, and can be attached to the wire 204 by a heat treatment, forexample, by heat shrinking the polymeric layer over the metal later andsome of the coils 208.

One or more holes 218 pass radially through both the sheath 213 and thegroup of adjacent coils 208 that are in contact with the sheath, suchthat the hole interrupts a portion of the coils. In some embodiments,pre-formed holes 219 can be made in the sheath 213 before the sheath isplaced on the coils 208 (FIG. 8), and then the holes 218 are cut throughthe coils 208, such as by a laser, after the sheath 213 is attached tothe cannula 200, using the pre-formed holes 219 in the sheath as aguide. In an alternative embodiment, a sheath 213 without pre-formedholes is attached to the coils 208, and the holes 218 are then madethrough both the coils 208 and sheath 213 at the same time.

In some embodiments, the sheath has an outer diameter less than or aboutthe same as an outer diameter of the polymeric coating. In suchembodiments, after the sheath has been attached to the coils, themaximum outer diameter of the cannula in the region of the holes is notincreased.

In some embodiments, the polymeric coating can be reformed over thesheath, while not obstructing the holes.

FIGS. 9 and 10 show a portion of a wire body 309 of another alternativespring cannula 300 in which a porous region 316 comprises a coil portion317 that is stretched apart axially, and a coating 314 having holes 318.

The coiled spring 300 includes the axially stretched coil portion 317,which is wound at a smaller angle relative to a longitudinal axis of thecannula 300 than the other adjacent coils such that it extends axiallybetween the markings 326 so as to provide enough space between the coilportion and the adjacent coils to later form holes in the sidewall ofthe cannula without cutting the coils. In some embodiments, the coilportion 317 is elongated in an axial dimension relative to adjacentcoils, such that a group of adjacent coils comprising the coil portion317 covers an axial distance greater than an axial distance covered by agroup of the same number of adjacent coils in other portions of thecannula 300. In some embodiments, the axial distance covered by the coilportion 317 can be at least as great as the axial length, or diameter,of a corresponding hole. In some embodiments, there can be two or moreholes adjacent to the coil portion 317, such as one hole on either sideof the coil. The two or more holes 318 placed adjacent to the coilportion can be axially and/or circumferentially offset from one another.In some embodiments, the coil portion 317 includes multiple coils, wherethe distance between the coils is sufficient to allow a hole to bepunched between the coil portions.

In some embodiments, the wire 304 is a stainless steel wire. In someembodiments, the wire is coated with a polymeric coating, for example,with a thermoplastic polyurethane elastomer such as Pellethane®. Afterthe coils 308 are wound, the wire can be heat-treated such that thepolymeric coating melts to form a coating that encases the coils 308,and forms the cannula 300. Holes 318 can then be made in the coating 314at locations commensurate with markings 326 on a mandrel 354, such thatthe holes 318 do not interrupt the coils 308.

As shown in FIG. 10, the generally cylindrical mandrel 354 has markings326 that are commensurate with the locations of the holes 318 that willbe formed in the resultant cannula 300. The markings can be holes in themandrel, raised knobs, pegs, a template or guide markings on the surfaceof the mandrel, or any other indicator that shows the locations wherethe holes will eventually be in the cannula. A wire 304 is wound aroundthe mandrel 354, to form coils 308. At least one coil portion 317 can beformed to prevent the coils from overlapping with the markings 304. Insome embodiments, the mandrel is pre-coated with a thin coating, such asa urethane tubing, prior to winding the wire 304, and an overcoat 311 isapplied after the wire 304 is wound. The mandrel is then heat andpressure treated to fuse the coatings together. However, the areas withthe coil portion may have decreased adhesive and weak kinkcharacteristics compared to adjacent tightly wound areas.

In another alternative embodiment, a mandrel around which the wire iswound can comprises pegs or projections on the radially outer surface ofthe mandrel. The pegs can have an outer diameter substantially equal tothe inner diameter of the desired holes. As the wire is wound around themandrel to form a plurality of coils, the wire can also be wound aroundthe projections so as to define the hole locations and reinforce theperimeter of the holes. The wire may or may not overlap itself in suchembodiments. In some embodiments, after winding, the projections can beremoved from the mandrel and then the mandrel is removed from theresulting coiled wire, resulting in a wire wound substantiallyconcentrically (except for any overlapping wire locations) about acentral axis, with sidewall hole locations defined by the wire.

FIG. 11 shows a distal portion of another spring cannula 400 in whichthe porous portions are transition sections 416.

The spring cannula 400 includes a wire body 409 having transitionsections 416 inserted between adjacent coils 408 of the wire body 409. Awire 404 makes up the wire body 409 and is continuous through thetransition sections 416 due to a coil portion 417 that extends at anangle across the transition section 416. The coil portion 417 is woundat a smaller angle relative to a longitudinal axis 406 of the cannula400 than its adjacent coils, creating a wire body 409 with a variablepitch. The coil portion 417 allows the wire 404 of the spring cannula400 to be continuous, without intervening cut ends by the transitionsections 416, helping to reduce and prevent cannula breakage, to provideadditional strength and to reduce the potential for process failures. Inaddition, the continuous wire 404 provides redundant wire support in thetransition sections 416. Transition sections 416 and the adjacent coilsof the wire 404 can be exposed to a localized heat and/or compression tofuse the transition sections and the adjacent coils together, furtherhelping to improve the bond strength between each of the transitionsections and the adjacent coils. The use of localized heating helps toreduce the amount of rework that may otherwise be required duringmanufacture. Further, the coil portion 417 provides additional surfacearea to increase bonding between the wire 404 and the transitionsections 416.

Each transition section 416 is tubular in shape and includes one or moreholes 418. In the illustrated embodiment, in each of the transitionsections 416, three holes 418 are evenly spaced circumferentially andthe holes 418 are axially aligned. However, the number of holes 418 ineach transition section 416 can vary depending on the application. Insome embodiments, the holes 418 are drainage holes to drain blood fromin and around the right heart of a patient during a cardiopulmonarybypass.

The coil portion 417 extends axially between the holes 418. In someembodiments, the coil portion 417 is elongated in an axial dimensionrelative to adjacent coils such that a group of adjacent coilscomprising the coil portion covers an axial distance greater than anaxial distance covered by a group of the same number of adjacent coilsin other parts of the cannula 400. In some embodiments, the axialdistance covered by the coil portion 417 can be at least as great as theaxial length, or diameter, of a corresponding hole. In some embodiments,there can be two or more holes adjacent to the coil portion 417, such asone hole on either side of the coil. The two or more holes 418 placedadjacent to the coil portion 417 can be axially and/or circumferentiallyoffset from one another. In some embodiments, the coil portion 417 is atleast the length of the transition section 416. In other embodiments,the coil portion 417 is shorter than the length of the transitionsection 416.

The transition sections 416 can be made of a thermoplastic polyurethaneelastomer (TPU), similar to the TPU used to form the overcoat 11 shownin FIG. 1. For example, the transition sections 416 can be made ofTecothane™. In some embodiments, the transition sections 416 can have adiameter equal to or about 22 French. Tecothane™ can provide a smoothertransition between the tightly coiled portions of the wire bodysurrounding the transition sections 416 than the previously usedmaterials used in the solid-wall tubes of prior non-continuous springcannulae, thus providing a superior feel to the spring cannula 400.

FIGS. 12A-12B show example transition sections 416, 416′ that can beused with the spring cannula of FIG. 11.

FIG. 12A shows one transition section 416 that can be inserted betweenadjacent coils of the wire 404. The transition section 416 includesholes 418 as described above and a groove 41 into which the coil portion417 can be inserted. The groove 41 provides a pathway for the coilportion 417 to stay in place and the groove 41 increases the surfacearea of contact between the coil portion 417 and the transition section416 to allow for increased bonding between the coil portion 417 and thetransition sections 416 when the transition section 416 and adjacentcoils are heated or compressed as discussed above.

The transition section 416 further includes overlap joints 42 on bothends of the tubular body of the transition section 416. The overlapjoints 42 have an outer diameter smaller than the central portion of thetransition section 416. The difference between the outer diameter of theoverlap joint 42 and the outer diameter of the central portion of thetransition section 416 is such that the coils 408 of the wire 404 canwrap around the overlap joint 42 without protruding past the outerdiameter of the central portion of the transition section 416 in anaxial direction. In some embodiments, the outer diameter of the overlapjoints 42 with coils 408 of the wire 404 wrapped around it issubstantially equal to the outer diameter of the central portion of thetransition section 416 to provide a continuous external diameter of thewire body 409. The overlap joints 42 increase the surface area betweenthe transition section 416 and the adjacent coils of the wire 404. Thus,when the transition section 416 and the adjacent coils of the wire 404are exposed to a localized heat or compression to fuse the adjacentcoils and the transition section together, the overlap joints 42 furtherhelp to improve the bond strength between the transition section 416 andits adjacent coils. In addition, the coil portion 417 will fuse with thegroove 41.

FIG. 12B shows another transition section 416′ that can be insertedbetween adjacent coils of the wire 404. The transition section 416′includes holes 418 and a groove 41 into which the coil portion 417 canbe inserted, as described above. The transition section 416′ does notinclude overlap joints, but has side surfaces 43 which will face sidesurfaces of the adjacent coils when the transition section 416′ isinserted between adjacent coils of the wire 404. When the transitionsection 416′ and the adjacent coils of the wire 404 are exposed to alocalized heat or compression to fuse the adjacent coils and thetransition section together, the side surfaces 43 of the transitionsection 416′ will fuse with the side surfaces of the adjacent coils. Inaddition, the coil portion 417 will fuse with the groove 41.

The angle of the groove 41 can vary in different embodiments. In theembodiments of FIGS. 12A-12B, the groove 41 is shown to have about a 45degree angle with respect to central axes of the transition sections416, 416′, which are coaxial with the central axis 406 of the springcannula 400. In other embodiments, the groove can be parallel with thecentral axis of the transition section, for example, to more easilyfacilitate punching the holes into the transition section.

The transition sections can be pre-cut to the desired size and to havethe groove 41. For example, a tube of thermoplastic polyurethaneelastomer, such as Tecothane™, can be positioned on a mandrel and ahelical slot cut along the tubing, the angle of the helical slotcorrelating to the angle desired for the groove 41. The tubing can thenbe cut into multiple transition sections. If overlap joints are desired,the ends of the cut transition sections can be further cut to reducetheir diameter.

There are various methods that can be employed to manufacture the springcannula 400. The manufacturing process generally includes joining thetransition section 416, 416′ with the wire body 409 and fusing themtogether with heat and/or pressure to make a consistent and continuoussection of wire body 409. The wire body 409 can them be attached to thetip 1 and the connector 3, and an overcoat 11 can be applied accordingto various suitable methods known in the art. Methods of manufacturingthe wire body 409 according to various embodiments of the invention arediscussed below.

FIGS. 13A-13D show a method of making the spring cannula 400 of FIG. 11.

As shown in FIG. 13A, the wire body 409 is provided that includes thecontinuous wire 404 formed into coils 408. The wire 404 has a coating414. The coating can be a polymeric material, for example, athermoplastic polyurethane elastomer such as Pellethane®, that is coatedon the wire 404 before the wire 404 is wound to form the wire body 409.After winding, the coated wire is heat-treated such that the polymericcoating on each coil bonds or fuses with the coating on the adjacentcoils and forms the substantially continuous, flexible coating 414 thatencases the coils 408. The helical coil may not have an additionalovercoat over the coating at this point.

The wire body 409 is cut using, for example, a blade 450, as shown inFIG. 13B. The blade 450 cuts between two adjacent coils 408, but doesnot cut through the wire 404. The blade 450 merely cuts the coating 414between two adjacent coils 408 to allow the adjacent coils to beseparated from each other yet still attached to each other via the wire404, as shown in FIG. 13C. The blade 450 or additional blades can beused to cut the wire body 409 in as many places as the number oftransition sections 416 desired.

Once cut, the wire body 409 can be pulled apart along a direction of acentral axis 406 of the wire body 409, creating wire reinforced regions407. Between the regions 407, spaces 452 are formed. The regions 407 arepulled apart from one another until the spaces 452 are of sufficientwidth to allow insertion of the transition sections 416. The spaces aretraversed by the wire 404 connecting the regions 407 on either side ofthe spaces 452.

As shown in FIG. 13D, the transition sections 416 are inserted into thespaces 452. The transition sections 416 can be pre-cut to include thegroove 41 for receiving the coil portion 417, can be pre-cut to includeholes 418, and can also be pre-cut to include the overlap joints 42. Toaccommodate the overlap joints 42, the wire body 409 is pulled apart toprovide sufficient space for the insertion of the transition sections416 including the overlap joints 42, and then after insertion of thetransition sections 416, regions 407 of the wire body 409 can be pushedtogether such that the coils 408 adjacent to the transition sections 416overlap the overlap joints 42. In other embodiments, the transitionsections can be pre-cut to include the side surfaces 43 instead of theoverlap joints 42 and in such embodiments, pushing the regions 407 ofthe wire body 409 closer together for overlapping may be unnecessary. Inalternative embodiments, the transition sections that are inserted maynot be pre-cut to include either a groove, holes, or overlap joints, ormore than one of these features.

Once the transition sections 416 are inserted, a mandrel can be insertedinto the wire body 409 and the transition sections 416 to hold thetransition sections 416 in position. In some embodiments, thetransitions sections 416 can be cut entirely through. The mandrel can beinserted through the wire body 409 first in these embodiments, and thecut transition sections 416 can be placed over the mandrel correspondingto the coil portions 417 thereafter. The tip 1 can be added to an end ofthe mandrel after the wire body 409 and transition sections 416 havebeen positioned around the mandrel. The transition sections 416 andadjacent coils of the wire body 409 can then be wrapped with afluoropolymer, such as a fluorinated ethylene propylene (FEP) film, andheat treated and pressure treated (e.g., such as via radial compression)to bond the transition sections 416 to the wire body 409. The tip 1 canalso be bonded to the distal end of the wire body 409 at this time. Inone embodiment, the wire body 409, the transition sections 416 and thetip 1, along with the PEP film, are heated using a hot box, such as aBeahm hot air bonder or similar heat treatment device. During the heattreatment, the cannula 400 can also be subjected to a constant rollingpressure or tension in order to imbed the coil portions 417 in thetransition sections 416. In embodiments where the transition sectiondoes not include a groove, this heating process will also melt thetransition section around the coil portion to surround the wire at thecoil portion and fuse the wire with the transition section. After thisbonding is complete, the heat and pressure can be removed and the FEPfilm can also be removed. At this point, various additional processingsteps similar to how previous cannula have been manufactured can beperformed, including punching holes 418 in the transition sections 416,adding an overcoat 14, and additional heat processing.

FIGS. 14A-14D show an alternative method of making the spring cannula400 of FIG. 11.

As shown in FIG. 14A, transition sections 416 are loaded onto a windingmandrel 454 at predetermined distances from each other according to thedistance desired in the final spring cannula 400. The tip 1 can also bepre-loaded onto the winding mandrel 454. The wire 404 is then tightlywound around the mandrel 545 until it reaches the first transitionsection 416, as shown in FIG. 14B. The wire 404 can be pre-coated with apolymeric material, for example, a thermoplastic polyurethane elastomersuch as Pellethane®. The first transition section 416 is then rotatedabout the winding mandrel 454 until the groove 41 lines up with the nextpart of the wire 404 to be wound. The wire 404 is then wrapped over thetransition section 416 in the groove 41, as shown in FIG. 14C. If a wirewrapping machine is used, the wire wrapping machine can be slowed toallow the transition sections 416 to be integrated, or a smart servomotor can be used to automate the process. The carriage or drive systemcan be programmed or adapted to form the variable pitch in the wirewinding at the transition sections 416. The wire 404 continues to bewound about the mandrel 454 after the first transition section 416, andthe same process used for the first transition section 416 is repeatedwhen the wire 404 reaches the more proximal transition sections 416.After the last transition section 416 has been integrated, the wire 404is wound about the mandrel 454 until the wire body 409 reaches a desiredlength. After winding is complete, the assembly can be placed into anoven, for example, an Accu-Heat oven, for curing and initial bonding.Then, localized zone heating and compression can be applied to the areasof the assembly corresponding to the transition sections 416, using, forexample, the Beahm hot air bonder, similarly as discussed in thepreviously manufacturing method. Afterword, various suitable additionalprocessing can be performed, including punching holes 418 in thetransition sections 416, adding an overcoat 14 and additional heatprocessing.

In the embodiments shown thus far, the wire segment that traverses thetransition sections is arranged at an angle. That is, the wire is woundaround the cannula to a certain degree over the transition sections. Inother embodiments, the wire traversing the transition sections can besubstantially straight, for example, as shown in FIG. 15B, with littleor no winding around the central axis of the cannula over the transitionsections, for easier manufacturing. However, the partially woundembodiments may be more stable and desirable, due to an increased wirebonding length.

FIGS. 15A-15B shows a modification of the steps of FIGS. 14B-14C inwhich a clamp 456 is included over the transition section 416.

According to this method, the transition sections (and optionally thetip 1) are pre-loaded onto the winding mandrel 454 and the wire 404 iswound around the mandrel 454 until it reaches the first transitionsection 416, as discussed regarding FIG. 14A. In this method, however,each of the transition sections 416, includes a clamp 456 covering it,as shown in FIG. 15A. The clamp 456 has an opening 458 to guide the wire404 as it crosses over the transition section 416. The opening 458 isaligned with the groove 41 of the transition section 416 in order toguide the wire 404 into the groove. However, in some embodiments, forexample as shown in FIG. 15A, the transition section does not have agroove and the clamp guides the wire 404 across the transition section416 without the aid of the groove.

The first transition section 416 can be rotated about the windingmandrel 454 until the opening 458 of the clamp 456 lines up with thenext part of the wire 404 to be wound. The wire 404 is then wrapped overthe transition section 416 with the aid of the clamp 456. Acyanoacrylate adhesive or thermal process can be applied to hold thewire 404 in place as it crosses over the transition section 416 in theopening 458 of the clamp 456. The wire 404 continues to be wound aboutthe mandrel 454 after the first transition section 416 and the sameprocess used for the first transition section 416 is repeated when thewire 404 reaches the additional transition sections, as shown in FIG.15B. Afterwards, the clamps 456 can be removed. Further processing canbe applied similarly as discussed with respect to the previousmanufacturing methods.

In a further embodiment, only a single clamp can be used and can bemoved from the first transition section to subsequent transitionsections, to aid in the wire crossing over each of the transitionsections.

FIG. 16A shows a distal portion of another spring cannula 500 includinga transition section 516 having an extended body. FIG. 16B shows theextended body of the transition section of FIG. 16A.

Similar to the embodiment of FIG. 11, the spring cannula 500 includes awire body 509 having transition sections 516 inserted between coils 508of the wire body 509. However, the spring cannula 500 varies from theembodiment of FIG. 11 in that the transition section 516 has anelongated body including a central region 55, and two end regions 57, asshown in FIG. 16B. The central region 55 includes a groove 51 forreceiving a coil portion 517 of the wire 504 and one or more holes 518.The groove 51 provides a pathway for an coil portion 517 of the wirebody 509 to stay in place and the groove 51 increases the surface areaof contact between the coil portion 517 and the transition section 516to allow for increased bonding between the coil portion 517 and thetransition sections 516 when the transition section 516 and adjacentcoils are heated or compressed as discussed above.

The end regions 57 of the transition section 516 have the same outerdiameter as the central region 55 and extend from the ends of thetubular body of the central region 55 to create a single uniform tubularbody. The end regions 57 increase the surface area between thetransition section 516 and the coils 508 of the wire 504 by providing awide area for coils 508 of the wire to overlap the transition section516, thus adding additional bond support. Thus, when the transitionsection 516 and the overlapping coils of the wire 504 are exposed to alocalized heat or compression, the overlapping coils and the transitionsection are fused together, helping to improve the bond strength betweenthe transition section 516 and the wire 504. This overlapping canprovide greater flexibility and resistance to kinking than traditionalcannulae.

The spring cannula 500 can be made similarly to the methods describedabove with respect to FIGS. 14A-15B. However, instead of stoppingwinding of the wire 504 around the mandrel when the transition section516 is reached, the wire 504 continues to be wound on the first endregion 57 of the transition section 516 until the wire 504 reaches andis aligned with the groove 51 at the central region 55. After the wire504 is positioned in the groove 51, the wire 504 is wound on the secondend region 57 of the transition section 516 until the end of thetransition section 516, and then proceeds to be wound on the mandrel.Further winding and additional fabrication proceeds similarly asdiscussed with respect to the previous manufacturing methods. If a clampis used according to the method of FIGS. 15A-15B, the clamp would onlycover the central region 55 of the transition section 516.

The continuously wound cannulae 400 and 500 provide redundant systems tokeep the cannulae together, while also reducing potential wire exposuredue to the decrease of the number of ends of the wire 404, 504. Thecannulae 400 and 500 have only two exposed wire ends, one at the tip andone at the connector; whereas prior cannulae had additional cut ends ateach of the solid-walled sections of the cannulae having holes punchedin them. The continuously wound cannulae 400 and 500 also allow for thewire to be continuously wound in a same direction, providing aconsistent orientation of the variable pitch wire. The processes formaking the cannulae 400, 500 also integrates multiple manufacturingsteps together and decreases the number of heat processing steps neededto add the tip, overcoat, and transition sections.

For example, various known cannulae are manufactured by a multiple stepmanufacturing process that involves at least three separate oven heatingsteps. In contrast, in the spring cannulae 400, 500, the manufacturingsteps are consolidated and the number of steps is reduced.

In a first manufacturing process, shown in FIG. 17, the winding step(51) includes winding the wire and incorporating the transition sectionsand tip, as discussed in detail above. The wire body is then placedthrough thermal heat processing, for example, by being heat treated inan oven, such as an Accu-Heat Oven, while wrapped in FEP (S2). The wirebody is then allowed to cool (S3) before being further subject tolocalized zone heating and compression (S4) to strengthen regions aroundthe transition sections. An overcoat is then applied (S5) and thecannula is again placed through thermal heat processing to cure theovercoat (S6). Afterword, the transition sections are hole punched (S7)and additional finishing steps are performed (S8). As shown, only twooven heating steps are used in manufacturing methods according toembodiments of the invention.

In another manufacturing process, shown in FIG. 18, the winding step(S101) includes winding the wire and incorporating the transitionsections and tip, similarly as discussed in the previous manufacturingmethod. An overcoat is then applied (S102), and the wire body with theovercoat is then subjected to localized zone heating and compression(S103) to bond and/or strengthen the regions around the transitionsections. The cannula is then placed through thermal heat processing,for example, by oven heating (S104). Afterword, the transition sectionsare hole punched (S105) and additional finishing steps are performed(S106). As shown, in this manufacturing process, only one oven heatingstep is used.

According to the embodiments of the invention, a cannula can bemanufactured by winding a continuous wire, without fully separating orsevering the wire. In addition, manufacturing methods can be used toreduce into a single winding step the previously separate steps ofincorporating solid-walled sections into the cut wire and incorporatingthe tip. As a result, the separate oven heating steps needed forincorporating these portions is likewise reduced.

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedisclosed methods, apparatuses, and systems should not be construed aslimiting in any way. Instead, the present disclosure is directed towardall novel and nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and sub-combinations withone another. The methods, apparatuses, and systems are not limited toany specific aspect or feature or combination thereof, nor do thedisclosed embodiments require that any one or more specific advantagesbe present or problems be solved.

Although the operations of some of the disclosed embodiments aredescribed in a particular, sequential order for convenient presentation,it should be understood that this manner of description encompassesrearrangement, unless a particular ordering is required by specificlanguage. For example, operations described sequentially may in somecases be rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed methods can be used in conjunction with other methods.Additionally, the description sometimes uses terms like “provide” or“achieve” to describe the disclosed methods. These terms are high-levelabstractions of the actual operations that are performed. The actualoperations that correspond to these terms may vary depending on theparticular implementation and are readily discernible by one of ordinaryskill in the art.

In view of the many possible embodiments to which the principles of thedisclosure may be applied, it should be recognized that the illustratedembodiments are only preferred examples and should not be taken aslimiting the scope of the disclosure. Rather, the scope of thedisclosure is defined by the following claims.

What is claimed is:
 1. A cannula comprising: a wire that is helicallywound to form a plurality of coils, wherein the plurality of coilscomprises at least one coil portion that is wound at a smaller anglerelative to a central axis of the cannula than adjacent coils positionedat opposite ends of the at least one coil portion; and an insertcomprising a porous section defining at least one hole passing radiallythrough the insert, wherein the insert is positionable between theadjacent coils and the at least one coil portion is positionable on theinsert and is spaced apart from the at least one hole.
 2. The cannula ofclaim 1, wherein the at least one hole does not interrupt any of thecoils.
 3. The cannula of claim 1, wherein the insert comprises a grooveand the at least one coil portion is positioned in the groove.
 4. Thecannula of claim 1, wherein the at least one coil portion extendsparallel to the central axis of the cannula.
 5. The cannula of claim 1,wherein the porous section of the insert defines three holes.
 6. Thecannula of claim 5, wherein the three holes are spaced apart from oneanother equally in a circumferential direction around the porous sectionof the insert.
 7. The cannula of claim 1, wherein the insert comprises athermoplastic polyurethane elastomer.
 8. The cannula of claim 1, whereinthe insert comprises a tubular body and overlap joints at opposite endsof the tubular body, wherein the overlap joints are configured to bepositioned radially inside the adjacent coils, such that the adjacentcoils overlap the overlap joints.
 9. The cannula of claim 8, whereinouter diameters of the overlap joints of the insert are smaller than anouter diameter of the tubular body of the insert.
 10. The cannula ofclaim 8, wherein the outer diameter of the cannula at the overlap jointsis greater than an outer diameter of other portions of the cannula. 11.A cannula comprising: a wire that is helically wound to form a pluralityof coils, wherein the plurality of coils comprises a first stretchedcoil portion that is wound at a smaller angle relative to a central axisof the cannula than adjacent coils positioned at opposite ends of thefirst stretched coil portion such that the first stretched coil portionis stretched axially relative to the adjacent coils; and an insertcomprising a first porous section defining at least one hole passingradially into the first porous section, wherein the first porous sectionis positionable along a length of the first stretched coil portion, witha portion of the wire defining the first stretched coil portionpositionable on the first porous section.
 12. The cannula of claim 11,wherein the portion of the wire defining the first stretched coilportion does not obstruct the at least one hole passing radially intothe first porous section.
 13. The cannula of claim 11, wherein the firststretched coil portion has a first stretched coil outer diameter whichis larger than outer diameters of adjacent coils positioned at oppositeends of the first stretched coil portion.
 14. The cannula of claim 11,wherein the plurality of coils comprises a second stretched coil portionthat is wound at a smaller angle relative to the central axis of thecannula than adjacent coils positioned at opposite ends of the secondstretched coil portion such that the second stretched coil portion isstretched axially relative to the adjacent coils.
 15. The cannula ofclaim 14, wherein the insert comprises a second porous section definingat least one hole passing radially into the second porous section,wherein the second portion section is positionable along a length of thesecond stretched coil portion, with a portion of the wire defining thesecond stretched coil portion positionable on the second porous section.16. A method of manufacturing a cannula comprising a wire that ishelically wound to form a plurality of coils, wherein the plurality ofcoils comprises at least one coil portion that is wound at a smallerangle relative to a central axis of the cannula than adjacent coilspositioned at opposite ends of the at least one coil portion, and aninsert comprising a porous section defining at least one hole passingradially through the insert, wherein the insert is positionable betweenthe adjacent coils and the at least one coil portion is positionable onthe insert and is spaced apart from the at least one hole, the methodcomprising: winding the wire to form the plurality of coils, includingthe at least one coil portion; and positioning the insert correspondingto the at least one coil portion between the adjacent coils.
 17. Themethod of claim 16, further comprising: bonding the insert with thewire.
 18. The method of claim 17, wherein bonding the insert with thewire comprises heating a region around the insert to bond the insertwith the wire.
 19. The method of claim 18, further comprising: heatingthe entire cannula to seal gaps between adjacent ones of the pluralityof coils.
 20. The method of claim 16, further comprising: applying anovercoat to the plurality of coils.